Real-time volumetric particle tracking velocimetry (VPTV) equipped with field-programmable gate array (FPGA) cameras has been used for open-space, low particle density, and large-scale airflow measurements with long measurement periods. However, the particle detection accuracy of FPGA cameras is inevitably hindered by non-uniform illumination, resulting in a reduction in the particle detection ratio and positional accuracy. In this article, we propose to use both synchronized FPGA and grayscale cameras in a VPTV system, where grayscale cameras utilize a new algorithm based on two-frame centroid and corner extraction (TFCCE) under non-uniform white-light illumination. To keep the frame rate of the FPGA cameras the same, the TFCCE algorithm was accelerated by a graphics processing unit (GPU). The simulation results showed that the 2D particle detection ratio of TFCCE was enhanced to approximately 80% with a positional accuracy of 0.57 pixels, compared to 30% and 0.94 pixels for the single-frame centroid extraction used in the FPGA. The GPU version of TFCCE was 15.09 times faster than the CPU version, resulting in a calculation time of 4.55 ms per image, compared to 68.70 ms when using the CPU. This system was also validated by the measurement of a turbulent jet flow in real-time at 120 fps. The experimental results correspond well with data published in the literature. Therefore, this new algorithm can improve VPTV systems in terms of particle detection ratio and positional accuracy in real time under conditions of non-uniform illumination.

People who live and work in air-conditioned rooms with micro-hypoxia are prone to sick building syndrome (SBS). Enriching oxygen into an air-conditioned room to increase the oxygen concentration can improve indoor air quality (IAQ) and reduce ventilation to save building energy consumption. In the present paper, the number and diameter of the oxygen supply vents, the oxygen supply flow rate, the oxygen supply method and the air flow organization form were comparatively studied using a numerical model. The results were compared with the experiments results in un-air-conditioned rooms, which showed that this model can give a favorable prediction. The results show that the maximum axial velocity decreases with the increase of the axial distance under air-conditioned conditions. The relationship between the oxygen-enriched area and the oxygen flow rate is obtained by fitting. The diameter of the oxygen supply pipe is 0.006 m, and when oxygen supply methods 1# and 4# are adopted, the oxygen-enriched area is F = 0.4 + 0.383 Q and F = 0.237 + 0.8 Q, respectively.

The large amount of computing data from hologram calculations incurs a heavy computational load for realistic full-color holographic displays. In this research, we propose a segmented point-cloud gridding (S-PCG) method to enhance the computing ability of a full-color holographic system. A depth camera is used to collect the color and depth information from actual scenes, which are then reconstructed into the point-cloud model. Object points are categorized into depth grids with identical depth values in the red, green, and blue (RGB) channels. In each channel, the depth grids are segmented into M×N parts, and only the effective area of the depth grids will be calculated. Computer-generated holograms (CGHs) are generated from efficient depth grids by using a fast Fourier transform (FFT). Compared to the wavefront recording plane (WRP) and traditional PCG methods, the computational complexity is dramatically reduced. The feasibility of the S-PCG approach is established through numerical simulations and optical reconstructions.

We propose using the Taylor Rayleigh-Sommerfeld diffraction method for point cloud gridding and RGB-D salient object detection to effectively improve the calculation speed. We have demonstrated the feasibility of these proposed methods through experiments.

We propose a holographic display system involving face recognition, air-writing, and multiple point cloud gridding encryption (M-PCGE) methods to provide multi-level security for objects. The feasibility of the proposed methods is confirmed by numerical reconstruction.